Deceleration Mode, Function - GF08.30-P-2004GRH

ENGINE 276.821 in MODEL 166 

The subfunction "Deceleration mode function" is considered and described from the point of view of the hybrid drive system.

We will not go into more detail here about internal signals and function sequences of the internal combustion engine and the regenerative braking system.

Function requirements for deceleration mode - general points 

• Hybrid drive system "READY"
• Accelerator pedal not operated
• Service brakes not operated
• Vehicle rolling
• Gear range "D"

Deceleration mode - general points 

If the brake and accelerator pedal is not actuated for a rolling vehicle, then:

• kinetic energy is taken up over the electrical machine (A79/1) and converted into electrical energy (regenerative braking) for a low charge level of the high-voltage battery (A100g1)
• A deceleration fuel shutoff of the internal combustion engine can also take place.

For a slightly actuated accelerator pedal, the electrical machine supports the adequately high charge level of the high-voltage battery of the system in order to counteract the falling vehicle speed.

If the brake pedal is actuated regenerative braking occurs.

In deceleration mode the following signals are read in by the ME-SFI [ME] control unit (N3/10):

• Accelerator pedal sensor (B37), accelerator pedal position
• Fully integrated transmission control unit (Y3/8n4) via the CAN network:
  • Gear range status
  • Wet clutch status
  • Transmission oil temperature signal
  • Status of the electric transmission oil pump (M42)
• Electronic Stability Program control unit (N30/4), via the CAN network:
  • Wheel speed
  • Service brake, status
• Battery management system control unit (N82/2) via the CAN network:
  • High-voltage battery voltage
  • Temperature of high-voltage battery
• Power electronics control unit (N129/1) via the CAN network:
  • Status of electrical machine
  • Torque of electrical machine
  • Rotational speed of electrical machine
  • Tolerable charging voltage/current signal

Function sequence for deceleration mode 

Depending on the charge level of the high-voltage battery and the selected transmission mode, the ME-SFI [ME] control unit calculates a nominal deceleration torque, which the ME-SFI [ME] control unit implements with deceleration fuel shutoff and/or regenerative braking in deceleration mode.

Cruising mode without use of the accelerator pedal 

If the brake and accelerator pedal are not actuated for a rolling vehicle and recuperation can take place, the internal combustion engine is disconnected from the engine in the transmission mode Individual "ECO" up to a speed > 180 km/h through opening the wet clutch of the drive and is switched off. If it is not possible for recuperation to take then the deceleration fuel shutoff of the internal combustion engine can also be activated.

For a slightly actuated accelerator pedal, the electrical machine supports the drive for an adequately high charge level of the high-voltage battery in order to counteract the falling vehicle speed.

Regenerative braking in deceleration mode 

Kinetic energy is taken up over the electrical machine and converted into electrical energy (regenerative braking) for a low charge level of the high-voltage battery. To do this the ME-SFI [ME] control unit requests a generative torque from the power electronics control unit via the hybrid CAN.

This actuates according to the request from the electrical machine.

Regenerative actuation of electrical machines and generates an AC voltage. This is converted by the power electronics control unit into a direct voltage and fed to the high-voltage battery.

In decel mode > 180 km/h or in transmission mode Sport the wet clutch remains closed and the internal combustion engine goes over into deceleration fuel shutoff and therefore generates a deceleration torque. The electrical machine supports this deceleration torque if necessary by a generative torque.

In deceleration mode and active deceleration fuel shutoff the internal combustion engine generates a boost torque which can be greater together with the recuperative boost torque than the calculated specified boost torque. In this case the deceleration fuel shutoff is not activated and the internal combustion engine generates a minimum actuatable torque. This concept ensures that the drive always remains the same for the driver as much as possible, with and without deceleration fuel shutoff.

The decel mode with deceleration fuel shutoff is more effective from an energy usage point of view. At a low charge level for the high-voltage battery and a low nominal deceleration torque is the higher deceleration regeneration braking with deceleration fuel shutoff is actually more meaningful.

	Deceleration mode electrical function schematic		PE08.30-P-2061-97NAH
	Overview of system components, hybrid drive system		GF08.30-P-9999GRH